Refining essential oils Episode n°1 : Fractional distillation or rectification

Tournaire Equipement, spécialiste des solutions de traitements des produits naturels à haute valeur ajoutée, propose des solutions d’extraction mais également de valorisations des produits extraits de plantes.

By Nicolas Tetard, Sales and Marketing Manager at Tournaire Equipement


Tournaire Equipement, a specialist in solutions for processing natural products with high added value, offers extraction solutions but also for the valorization of products extracted from plants. One of the products commonly obtained in the field of natural products is crude essential oil. This is a variable mixture of different volatile compounds that sometimes need to be reworked.

In terms of refining crude essential oils, two solutions are generally considered:

1.Fractional distillation or rectification

2.Molecular distillation

In this first episode, we will focus on the fractional distillation process, also called rectification.

The process of fractional distillation (or rectification) separates the different components of a product (such as essential oils) into fractions. Each fraction can then be analyzed (by GC analysis) and, depending on its value, can be retained or rejected. The selected fractions can then be combined to obtain a purified essential oil with high added value, free of “pollutants”.

Principle :

The separation of the components is based on their difference in boiling temperature: the essential oil is separated by heating it to a temperature at which only a specific fraction vaporizes. The “heavy” components (high boiling point) remain in the liquid state in the boiler, while the “lighter” ones (low boiling point) turn into steam. The steam created passes through a column filled with structured packing, which further improves the separation of components. The lightest components of the vaporized fraction reach the top of the column, while the heavier ones tend to remain at the bottom of the column.

A racking system, at the top of the column, recovers some of the lightest components in a series of flasks. Since the lighter components are extracted from the top of the column, they give way to other heavier components, which in turn reach the top of the column and are extracted in different flasks. The process is continued until many different fractions are extracted.

Equipment :

In terms of equipment, Tournaire Equipement designs rectification columns with continuous and discontinuous operation. Our equipment ranges from pilot size to industrial production unit. As an example, we offer rectification columns equipped with a boiler with a capacity of 40 L and up to 15 m3 – any intermediate capacity being feasible. We offer precisely engineered solutions that allow the perfect control of the quality level of the final product. These include columns with high-quality structured packing (Sulzer type) offering up to 120 theoretical plates.

Depending on the product to be processed, we offer columns that operate either at atmospheric pressure, for example for solvent regeneration, or under vacuum, up to 1 mbar absolute. Some columns are also equipped with a falling film heating system that has the major advantage of significantly reducing the degradation of heat-sensitive products. Finally, our equipment comes with perfectly tuned automation for smooth operation.

Example of application :

An example of the use of fractional distillation is the readjustment of the linalool/linalyl acetate ratio in lavender essential oil to make it comply with European standards. Some types of lavender provide essential oils containing a greater amount of linalool than linalyl acetate, which is not in line with customer expectations. Fractional distillation isolates and rejects the linalool-rich fraction.

Testing and development :

Each product is unique and requires a tailor-made solution to ensure a high-quality result. Through its collaborative testing and development platform, the WiNatLab, Tournaire Equipement supports you in the development of your products by defining a finely tuned equipment adapted to the desired goal. Tests on pilot rectification equipment are also possible.

To learn more, visit the WiNatLab page.